public string GetDiscipline()

{
  var bsl_discipline = MapView.Active.Map.GetLayersAsFlattenedList().OfType<BuildingDisciplineSceneLayer>().FirstOrDefault(l => l.Name == "Architectural");
  var disciplineName = bsl_discipline.GetDiscipline();
}

{
  var bldgLayer = MapView.Active.Map.GetLayersAsFlattenedList().OfType<BuildingSceneLayer>().First();
  var disciplines = new Dictionary<string, BuildingDisciplineSceneLayer>();
  //A Building layer has two children - Overview and FullModel
  //Overview is a FeatureSceneLayer
  //Full Model is a BuildingDisciplineSceneLayer that contains the disciplines

  var fullModel = bldgLayer.FindLayers("Full Model").First()
                                 as BuildingDisciplineSceneLayer;

  //collect information on the disciplines
  var name = fullModel.Name;

  var discipline = fullModel.GetDiscipline();
  //etc
  //TODO - use collected information

  disciplines.Add(discipline, fullModel);

  //Discipline layers are composite layers too
  foreach (var childDiscipline in fullModel.Layers
                      .OfType<BuildingDisciplineSceneLayer>())
  {
    //Discipline layers can also contain FeatureSceneLayers that render the
    //individual full model contents
    var content_names = string.Join(", ", childDiscipline.Layers
         .OfType<FeatureSceneLayer>().Select(fl => fl.Name));
    // Recursively call this "function" to go deeper
  }
}